The state's top consumer advocate is accusing Connecticut Light & Power of submitting manipulated evidence and dishonest testimony to utility regulators regarding its controversial $221 million rate case.

Seeking sanctions against the state's largest public utility, the Office of Consumer Counsel has asked state regulators to strike testimony by a company consultant who testified in support of a large increase in depreciation costs and who, according to the agency, made exceedingly rosy claims about his track record on rate cases.

As part of her request, Consumer Counsel Elin Swanson Katz is asking regulators both to prohibit the company from recouping costs it incurred in defending itsrate case and to cut the company's profit margin by 0.35 of a percentage point. Reached by phone Monday, Katz said the motion speaks for itself and it is the responsibility of the state Public Utilities Regulatory Authority to decide the necessary sanctions.

The depreciation costs are incremental payments for new electrical equipment; the installation and retirement of items like poles and wires combined with the rate that that equipment loses value all factor into depreciation expenses, which the CL&P consultant testified should increase by $31.4 million in the new rates.

To bolster that conclusion, the consultant, John Spanos of Gannett Fleming, who said he has stood before dozens of public utility regulators in more than 170 cases, testified: "All commissions have accepted the studies I have performed."

Incredulous at the statement, the Office of Consumer Counsel later asked: "So you are saying that your methodologies, your estimates, they've never been criticized by or differed with by a commission before which you've appeared?"

"Not by a commission," Spanos responded.

This launched a lengthy fact-checking episode for the Office of Consumer Counsel, which asked for the last 10 cases Spanos testified in around the United States, looking for indications that the evidence he entered in those cases were challenged or changed in some way.

CL&P returned "selective portions of those documents," with blocks of text whited-out or cut from the pages, officials said in the motion to the state Public Utilities Regulatory Authority. They asked for the full documents, most of which the company provided later or attorneys found on the websites of public utilities commissions.

One example cited by the consumer office is a recent rate case heard by the Kentucky Public Service Commission. The initial document CL&P provided was a single paragraph on an otherwise whited-out page that stated that the rates the utilities proposed "shall be effective."

The entire document, which CL&P later sent to regulators and the consumer office, showed that the utility's depreciation rates were reduced by nearly $20 million.

In another, for Potomac Electric Power Co., regulators reduced the $5.7 million increase for depreciation expenses to $3.4 million. CL&P initially submitted a single paragraph describing Spanos' work in this rate case. It looked cobbled together, a block of text from the bottom of one page and the top of another pasted onto one sheet.

"Efforts were taken to photocopy and paste together into one page a single, non-controversial paragraph," the consumer advocate said.

In its motion, the Office of Consumer Counsel claims Spanos "did not testify accurately or honestly" about how other jurisdictions have accepted his depreciation studies. And further, the consumer office says, the first round of documents were "manipulated to exclude impeaching text and was misrepresented as being complete."

CL&P, a division of Northeast Utilities, disputed the Office of Consumer Counsel's claim, in a statement from spokeswoman Tricia Taskey Modifica on Monday. She declined to answer questions relating to the initial, selective filings.

"Unfortunately, the [Office of Consumer Counsel] has made a false and baseless claim against our expert witness. John Spanos has a long history working in depreciation studies for utilities and providing counsel to commissions around the country as they consider rate cases," the company said, adding that it plans to file a formal response to regulators on Tuesday.

Katz said in the filing: "While rate cases are often litigious by nature, and zealous advocacy is to be expected, when a line is crossed indicating intentional manipulation and mischaracterization of evidence, PURA must act with authority to indicate such actions will not be tolerated."